Originally Posted by crankyusi
Bummer, since I think that if I flew California to Oregon there would be no formal customs in Oregon for that. Thanks again.
Correct, but you are comparing two different setups. CA -> OR, you are going from a state to another state thus there is no "import" tax since you are not leaving the US. US -> Guam you are actually leaving the country. While it is a territory of the US it is not actually a state in the US and therefore CAN subject the import to duty. I believe it can't by law be any worse then with any other foreign country. They also have to option of not charging taxes also. Just remember territories operate as their own "country" (with some restrictions) untill they become a state.